Both complete beginners and people who have been drawing for years find learning to draw in a right-brained way quite a revelation.
It came from Sam Marshall, who taught us once a week in the first year and painted full time the rest. He was a broad Northerner, and would run around waving his arms at the view in front of us shouting “Look at the negative spaces!!!!” I will never forget that, and try to emphasise it as much as I can with my own students.
If you have a problem seeing that, remember the idea of everything being ‘flat’ (see previous blogs); the legs further away will ‘touch’ the closer ones higher up on the picture plane. We know that chairs have a flat, probably square, seat - but that square will be in perspective, so it will not appear square at all. By drawing the negative spaces in between the legs, and those around the seat, your drawing will look three dimensional and very realistic.